HC-49S-8MHz-20pF
Standard HC-49/S 8MHz crystal resonator with 20pF load capacitance, ±30ppm tolerance for microcontroller applications.
Product Overview
Description
This 8MHz crystal provides a stable clock source for 8-bit and 32-bit microcontrollers. The HC-49/S package offers excellent mechanical stability and is compatible with standard through-hole assembly processes.
With ±30ppm frequency tolerance and 20pF load capacitance, this crystal is suitable for most general-purpose microcontroller applications including UART communication at standard baud rates.
The industrial temperature range of -40C to +85C ensures reliable operation in harsh environments. The low-profile HC-49/S package is ideal for applications requiring through-hole mounting with height constraints.
Product Series
HC
Primary Application
Microcontroller clock
Key Features
- 8MHz standard frequency
- HC-49/S package
- ±30ppm tolerance
- Industrial temperature
Specifications
| Frequency | 8.000 MHz |
|---|---|
| Frequency Tolerance | ±30ppm at 25C |
| Frequency Stability | ±50ppm over -40C to +85C |
| Load Capacitance | 20pF |
| Equivalent Series Resistance | 60 ohms max |
| Drive Level | 100uW max |
| Aging | ±3ppm per year max |
| Operating Temperature | -40C to +85C |
| Storage Temperature | -55C to +125C |
| Package | HC-49/S (11.0 x 4.7 x 3.5mm) |
Applications
Microcontroller clock
Industrial automation and control
UART communication
Communication and interface
Industrial control
Industrial automation and control
Consumer electronics
Consumer electronics
FAE Expert Insights
"I highly recommend the HC-49S-8MHz-20pF for general-purpose microcontroller applications. In my experience supporting numerous embedded designs, this crystal delivers consistent performance at an excellent price point. The 20pF load capacitance is compatible with most MCU oscillator circuits, and I have found the ±30ppm tolerance adequate for standard UART baud rates up to 115200. The HC-49/S package is robust and easy to handle during assembly. For industrial applications, the -40C to +85C temperature range provides reliable operation. I always recommend using NP0/C0G ceramic capacitors for the load capacitors to ensure temperature stability. At under $0.04 in volume, this crystal offers outstanding value for cost-sensitive designs."
Reliable 8MHz crystal with excellent cost-performance ratio for MCU applications
— Michael Chen, BeiLuo
Frequently Asked Questions
What load capacitors should I use with this crystal?
For the 20pF load capacitance specification, calculate external capacitors as follows: CL = (C1 * C2) / (C1 + C2) + Cstray. With Cstray typically 3-5pF, you need (C1 * C2) / (C1 + C2) = 15-17pF. Using C1 = C2, each capacitor should be 30-34pF. Standard values are 33pF. Use NP0/C0G ceramic capacitors for temperature stability. Place capacitors as close to the crystal as possible to minimize stray capacitance. Always verify the actual oscillation frequency and adjust if necessary.
Use 33pF NP0 ceramic capacitors. Contact us for circuit design review.
Can this crystal be used for USB applications?
For USB applications, the 8MHz frequency can be used if your MCU has a PLL that can multiply 8MHz to 48MHz for USB clock. However, USB typically requires ±2500ppm (0.25%) accuracy, and this crystal's ±30ppm tolerance is more than adequate. Check your MCU datasheet to confirm it can generate 48MHz USB clock from 8MHz input. Some MCUs require 12MHz or 48MHz crystal directly for USB. If your MCU supports PLL from 8MHz, this crystal will work well. For direct 48MHz USB clock, consider the HC-49S-48MHz-20pF instead.
Verify your MCU can generate USB clock from 8MHz. Contact us for USB clock recommendations.
What is the maximum drive level and why does it matter?
The maximum drive level for this crystal is 100uW (microwatts). Drive level is the power dissipated in the crystal during oscillation. Exceeding the maximum drive level can cause: 1) Frequency shift - the crystal may oscillate at a different frequency. 2) Accelerated aging - long-term stability degradation. 3) Crystal damage - permanent damage in extreme cases. 4) Unreliable startup - difficulty starting oscillation. Most modern MCUs have low-power oscillator circuits that typically drive crystals at 10-50uW, well within the 100uW limit. If using a discrete oscillator circuit, ensure the drive level is measured and within specification.
Verify drive level in your circuit design. Contact us for drive level measurement guidance.
How do I verify the crystal is oscillating at the correct frequency?
To verify crystal frequency: 1) Use a frequency counter with high-impedance probe to avoid loading the crystal. 2) Measure at the oscillator output pin, not directly on the crystal pins. 3) Compare measured frequency to specified 8MHz ±30ppm (7.99976 to 8.00024 MHz). 4) Measure at operating temperature if possible. 5) Allow the circuit to warm up for stable readings. 6) Check for stable oscillation - frequency should not drift significantly. If frequency is off, check load capacitors and adjust if necessary. If crystal does not oscillate, check ESR compatibility and oscillator circuit gain.
Use high-impedance frequency counter. Contact us for frequency measurement assistance.
What is the difference between HC-49/U and HC-49/S?
HC-49/U (Universal) and HC-49/S (Short) are similar packages with slight differences: HC-49/U - Full height package (11.0 x 4.7 x 4.0mm), slightly taller profile. HC-49/S - Low profile package (11.0 x 4.7 x 3.5mm), 0.5mm shorter. Both have identical electrical characteristics and pinout. HC-49/S is more common in modern designs due to lower height profile. HC-49/U may be preferred for hand soldering due to slightly larger body. The /S variant is interchangeable with /U in most applications. This product uses the HC-49/S low-profile package.
HC-49/S is recommended for most applications due to lower profile. Contact us for HC-49/U if needed.